SiC MESFET Rajesh C. Panda EEL 6935 WBG I Spring 2003

Outline Introduction Literature Review Theory of MESFET Operation Advantage of SiC MESFET SiC Basic MESFET Structure MESFET Specifications SiC MESFET Application Summary

Literature Review K. P. Hilton, M. J. Uren, D. G. Hayes, P. J. Wilding, H. K. Johnson, J. J. Guest and B. H. Smith, "High power microwave SiC MESFET technology", in Workshop on High Performance Electron Devices for Microwave and Optoelectronic Applications, EDMO, 1999, pp S.T.Allen, J.W.Palmour,,C.H.Carter,Jr., C.E.Weitzel, K.J.Nordquist, and L.L.Pond, III, “Silicon Carbide MESFET’s With 2 W/mm and 50% P.A.E. at 1.8 GHz ” IEEE MTT-S Symposium Digest, San Francisco, CA, June, 1996, pp ST Allen, RA Sadler, TS Alcorn, JW Palmour, CH Carter, "Silicon Carbide MESFET‘s for High Power S-Band Applications”, 1997, IEEE MTT-S Digest, pp SP Murray and KP Roenker, “An Analytical Model for SiC MESFETs,” Solid State Electr. vol. 46 (10), pp , October KE Moore, CE Weitzel, Kevin J. Nordquist, Lauren L. Pond, III, John W. Palmour, Scott Allen, and Calvin H. Charter, Jr., “ 4H-SiC MESFET with 65.7 % power added efficiency at 850 MHz”, IEEE Electron Device Letters, Vol.18, No.2, February Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A Wiley-Interscience Publication, 1988.

qΦ s qχ s EcEc EFEF EVEV qΦ m ЄFЄF Metal n-Type s.c. qΦ b Metal n-Type s.c. qV bi Energy-band Diagram before contact Energy-band Diagram after contact Theory Of MESFET Operation qΦ m = Metal Work FunctionqΦ s = Semiconductor Work Function qχ s = Semiconductor Electron AffinityReference Energy Level (Vacuum) Schottky-barrier formed when metal deposited on semiconductor Ref: Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A Wiley- Interscience Publication, 1988

Theory Of MESFET Operation N+N+ N+N+ Semi-Insulating Substrate Depletion Region Neutral Region Gate Source Drain n Ref:

Theory Of MESFET Operation S G D DR - V GS controls channel (DR) V DS drifts carriers Fully depleted channel = pinch off condition (V pinch ) Depletion region forms under schottky contact (gate) and controls the flow of current in the channel (n-type) layer. Device therefore behaves as voltage controlled switch, capable of very high speed modulation. Ref: Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A Wiley- Interscience Publication, 1988

Theory Of MESFET Operation Ref: Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A Wiley- Interscience Publication, 1988

Theory Of MESFET Operation Drain Voltage Drain Current V GS = -1 V GS = -0.5V GS =0

Advantage of SiC MESFET Wide Energy Band Gap Device High Breakdown Electric Device High Electrical and Thermal Conductivity High Saturated Electron Velocity High Melting Point Chemically Inert Ref:

Advantage of SiC MESFET Ref:

SiC Basic MESFET Structure SourceDrain Gate (Schottky) N+ Epi N-Channel P-Buffer N-type Substrate Active Layer High Resistive Substrate Contact Layer Ref:

Ref: S.P. Murray and K.P. Roenkar, “An Analytical Model For SiC MESFETs ”.

MESFET Specifications Ref:

MESFET Specifications Comparison of SiC and GaAs MESFET Specifications: Drain Source Voltage and Drain Saturation Current –SiC devices have a higher VDSS and a higher IDSS than GaAs devices thereby increasing the power handling capabilities of SiC MESFETs Maximum Frequency –SiC fmax is approximately ten times greater than that found in GaAs devices Device Power Dissipation –SiC MESFET thermal dissipation greatly exceeds that of GaAs which allows for greater power handling and higher temperature operation

SiC MESFET Application The Major Applications Include : Wireless Communication Microwave Circuits High Power High Frequency Power Amplifiers Ref:

Summary The Superior Properties of SiC MESFET like higher breakdown voltage, higher thermal conductivity and higher saturated electron velocity makes it one of the most promising devices for high frequency and high power.